1. Field of the Invention
Embodiments disclosed herein relate to wireless transmit and receive systems. More specifically, embodiments herein may relate to a directional diversity receive system.
2. Description of the Related Art
A traditional radio frequency (RF) link consists of both a transmit and receive system. Such RF link may use the digital COFDM (Coded Orthogonal Frequency Division Multiplexing) modulation/demodulation schemes to transmit and/or receive audio, encapsulated data, compressed video, or other information or data. The transmit system takes the information and converts it into a modulated RF signal using a transmitter and radiates that energy into the air via an antenna. The receive system uses an antenna to collect the RF energy and feed it to a receiver which then demodulates the signal back into the original information.
Between the output of the transmit antenna and the input of the receive antenna, the RF signal propagates through the air getting attenuated and bounced off terrain, buildings, or water. As received at the receive antenna, the signal typically should have enough power (from the transmitter) and gain (from the receive antenna) to overcome the attenuation due to the air and to satisfy the threshold signal level required by the receiver. Attenuation due to the air is dependent on a number of factors, such as distance traveled, frequency of the signal (higher frequency signals generally get attenuated more), and atmospheric conditions (hot/cold and dry/wet air may all affect the attenuation). The attenuation can be roughly calculated, but greater attenuation called fading may occur under certain conditions. Such greater attenuation must be accounted for when designing receive systems.
In addition, the receive system may also receive none, some, or all of the bounced signals, which is known as natural multi-path. This natural multi-path presents multiple images of the same signal at the receiver due to paths having varied lengths which are taken by the bounced signals to get from the transmit antenna to the receive antenna. In addition, the system may receive other transmitted signals of the same, or similar, frequency and power levels, known as unnatural multi-path. To receive a desired signal, the system can preferably discriminate against and overcome both forms of multi-path to demodulate the desired signal.
Problems further to those described above may also be experienced when receiving a signal. For example, too much received signal, be it a desired signal or signal from natural and/or unnatural multi-path, can be a problem due to an input amplifier of the receiver being driven into a non-linear region and causing unrecoverable distortions of the desired signal.
A need exists for improved wireless communication systems and methods, for example for use with the transmission and reception of RF signals. More specifically, a need exists for improved receive systems and methods of controlling those receive systems.